In maths, it can be very frustrating when pupils get the answer wrong when we know that they understand how to carry out a particular calculation. This can often be due to a careless error that a pupil has overlooked since they are not asking themselves, ‘Is this answer reasonable?’For this reason, it is useful to look at questions and answers and ask pupils to explain why particular answers cannot be correct, without carrying out the actual calculation. That is the focus of this PowerPoint pres